Gerard W. Ostheimer “What's New in Obstetric Anesthesia” Lecture

BEGINNING in 1975, a review of the preceding year's medical literature relevant to obstetric anesthesiologists has been presented at the Annual Meeting of the Society of Obstetric Anesthesia and Perinatology. In 1995, the lecture was renamed in honor of Dr. Gerald Ostheimer. Dr. Ostheimer was a Boston obstetric anesthesiologist known for considerable contributions to research and education. The 2007 Ostheimer lecture was based on a review of medical literature published between January and December 2006, with the goal of identifying articles relevant to obstetric anesthesia practice. This year's review identified 1,637 articles in 52 journals in the field of anesthesiology and obstetrics (appendix).The content areas covered by these articles included obstetric complications (25% of total), maternal coexisting disease (20%), fetal and neonatal disease (17%), labor analgesia (14%), anesthetic complications (4%), cesarean delivery anesthesia (3%), and miscellaneous topics (18%). Topical areas presented in 2006 included morbidity related to inflammation during pregnancy, genetic polymorphisms and outcomes, primary elective cesarean delivery and vaginal birth after cesarean trials, maternal obesity, global maternal health, reduction of multiple gestations with assisted reproductive technologies, and the recurring themes of preterm delivery and preeclampsia. The objective of this review of the 2006 literature was to present key articles published in the areas of maternal coexisting disease, labor analgesia, anesthesia for operative delivery, obstetric complications, anesthetic complications, and postpartum issues.Obesity is now a public health issue in most developed countries. Ogden et al. ,1in the Journal of the American Medical Association , reported on obesity incidence among women of reproductive years. In this study by the Centers for Disease Control and Prevention, three biannual results between 1999 and 2004 of the National Health and Nutrition Examination Survey were compared. This population-based survey examines the health of a randomly sampled group of children between the ages of 2 and 19 yr and adults aged 20 yr and older, which represent the US population. Information was extracted from the study on women during reproductive years (12 yr and older). A graphic illustration of this data is presented in figure 1and illustrates the impressive proportion of the female population within each age group who are defined as overweight or obese. Almost 30% of women 20 yr or older are obese, defined as a body mass index (BMI) of greater than 30 kg/m2. This proportion of the female population has seemed to stabilize during the 6 most recent years of survey examination. Perhaps the recent media attention on this disorder has increased the population's awareness to a level that will prevent further increases.A study that specifically addressed the issue of obesity among the pregnant population was from Helms et al. 2These investigators retrospectively studied the weight gain of almost 1.5 million parturients in North Carolina with singleton, term gestations between the years of 1988 and 2003. Excessive weight gain was defined as more than 40 lb gained during pregnancy. During the time period studied, the proportion gaining excessive weight increased from 15.5% in 1988 to 19.5% in 2003. A goal of the 2010 Healthy People Report, specifically goal 16-12, is to “increase the proportion of mothers who achieve a recommended weight gain during their pregnancies.”†This study would suggest that this goal has not been achieved. Women with excessive weight gain were more likely to have macrosomic babies than the rest of the population (adjusted odds ratio, 1.9; 95% confidence interval [CI], 1.85–1.93) and had an increased risk of primary cesarean delivery (adjusted odds ratio, 1.5; 95% CI, 1.45–1.51).Obese parturients are at increased risk for medical and obstetric complications during pregnancy, and there is evidence that anesthetic difficulties can arise for these patients as well. Technical difficulties with provision of neuraxial anesthetic techniques are well known, as are problems with ventilation after induction of general anesthesia. Recent research has focused on differences in anesthetic requirements for the obese population. In a study of analgesic requirements during labor, Panni and Columb3determined the minimum local anesthetic concentration (MLAC) of bupivacaine. Women were placed into one of two groups based on BMI: a BMI of 30 kg/m2or less or a BMI of greater than 30 kg/m2. The women studied were at term gestation, in established labor, requesting labor epidural analgesia. They received a specific bupivacaine concentration for initiation of labor analgesia depending on the previous woman's success. Success was defined as a reduction of visual analog pain score of 10 mm or less (out of 100 mm) within 30 min of epidural initiation. The study used an up-down sequential allocation technique to determine the MLAC of bupivacaine for both groups. The MLAC for obese women was reduced by 41% compared with women with a BMI of 30 kg/m2or less (bupivacaine MLAC BMI >30 kg/m2: 0.067% [95% CI, 0.048–0.086%]; bupivacaine MLAC BMI ≤30 kg/m2: 0.113% [0.108–0.118%]). Despite a reduction in local anesthetic concentrations, the upper extent of sensory block to ice was found to be higher in the obese group (BMI >30 kg/m2: T8 [25th-75th quartile, T6–T10]; BMI ≤30 kg/m2: T10 [T10–T12]). It seems that there is a greater distribution of epidural local anesthetic in the obese parturient, because the pain scores at time of request were no different between the groups. The appreciation of altered epidural anesthetic requirements for labor in the obese parturient needs to be incorporated into our clinical plan for this group.The latest Confidential Enquiries into Maternal Deaths has reported that cardiac disease is now the most commonest cause of maternal death.4Ischemic heart disease has been responsible for approximately 30% of Confidential Enquiries cardiac deaths reported between 1991 and 2002. Two studies, one from the United States and one from Canada, report on population-based estimates of the incidence of myocardial ischemic disease among pregnant women.5,6The incidence rate for this disease was described as 6.2 per 100,000 deliveries in the United States and 1.1 per 100,000 women delivering in Canada. The difference between each country's rates may be attributable to differences in ascertainment of cases. The American study identified myocardial ischemic disease into the postpartum period, whereas the Canadian study only identified cases among women admitted to hospital for delivery. Both studies documented similar maternal case fatality rates (United States: 6.2%; Canada: 1.8%) and identified similar maternal factors associated with ischemic events (maternal age >30 yr, hypertension, and diabetes). Although this disease is a rare event, the combined number of maternal deaths from arterial events, including ischemic heart disease and aortic dissection, almost exceed that of maternal deaths due to venous thromboembolism. In the latest Confidential Enquiries into Maternal Deaths in the United Kingdom, 31 women died due to myocardial ischemia, cerebral ischemia, or aortic dissection, compared with 33 women with deaths from pulmonary embolism.4Considerable attention has been given to reducing deaths due to venous causes, and the same initiative should be applied to the early recognition and therapy for arterial events.Peripartum cardiomyopathy developing within the last months of pregnancy or within the first 6 months after delivery has been closely studied in a unique population on the island of Haiti.7Fett et al. 7prospectively followed up 99 women with peripartum cardiomyopathy and documented the effect of further pregnancies on their cardiac function. Fifteen of 99 women became pregnant again, with only 1 of the 15 women regaining normal ventricular function before the subsequent pregnancy. More than 50% of the women (8/15) had a decline of ventricular function during the subsequent pregnancy. Within this group, mean estimates of left ventricular ejection fraction at 1 yr from the index pregnancy were 38% and declined to less than 30% at 4 yr. However, the 7 of 15 women who did not have a deterioration of heart function in the subsequent pregnancy eventually regained normal left ventricular function after delivery. The time to normal ventricular function was not limited to the first 6–12 months but continued out for several years. Although these findings are in contrast to previous descriptions of the natural order of the disease, their generalization to populations outside Haiti needs to be confirmed.Labor analgesia was the most common topic studied in 2006 in obstetric anesthesia literature. There were contributions that refined systemic, neuraxial, and nonpharmaceutical techniques of labor analgesia. Published in the Cochrane Library collection of evidence-based literature was a systematic review of complementary and alternative therapies for pain management in labor.8This meta-analysis of 14 studies evaluated the efficacy of acupuncture, acupressure, audioanalgesia, aromatherapy, hypnosis, massage, and relaxation for labor analgesia. Only two therapies were found to be beneficial, acupuncture and hypnosis. Two randomized studies involving acupuncture compared with no treatment found a 30% reduction (95% CI, 0–51%) in the use of further pharmacologic therapies, but maternal satisfaction seemed to be no different. Hypnosis was shown to reduce use of epidural analgesia by 70% among 520 women randomly assigned to hypnosis or supportive psychotherapy in the United States. These two particular therapies require advance planning for parturients to make them available at the time of their labor and delivery.Discussion of epidural analgesia for labor often takes place with patients in the antenatal setting; however, the consent for the procedure is obtained just before administration in labor. Anesthesiologists with an interest in obstetric anesthesia were surveyed about the risks they discussed with patients in the antenatal setting compared with during labor.9Approximately 60% of the Obstetric Anesthesia Special Interest Group of the Australian and New Zealand College of Anesthetists responded to the survey, and the top five risks presented before or during labor respectively were post-dural puncture headache (96/86%), epidural block failure (93/78%), permanent neurologic injury (90/78%), leg weakness (79/68%), and hypotension (78/63%). The survey also included questions on the complication rates quoted to the patient, and these were often inaccurate compared with the published rates. An excellent summary table is included in the article, which incorporated the published rates of the 20 mentioned possible anesthetic risks.Several articles addressed technical aspects of neuraxial anesthetic delivery systems. Wong et al. 10evaluated the differences between administering the hourly background epidural solution as a continuous infusion or as two quick boluses during the same time period, among multiparous women undergoing induction of labor in a randomized, double-blind study. The primary outcome was the dose of bupivacaine consumed per hour, as well as secondary outcomes of patient satisfaction, labor pain scores, number of and delivery of patient-controlled epidural analgesia (PCEA) requests. After the initiation of analgesia with a combined spinal-epidural technique (CSE), parturients receiving epidural boluses of 6 ml every 30 min consumed less bupivacaine (median, 10.5 mg/h; 95% CI, 9.5–11.8 mg/h) than women receiving a background bupivacaine infusion of 12 ml/h (median, 12.3 mg/h; 95% CI, 10.5–14.0 mg/h). Of interest, this increase in consumption was most significant among women with longer labors. Patient satisfaction was higher with the scheduled boluses and perhaps reflected the ability of this technique to better distribute the solution through the epidural space. Unfortunately, at the current time, pump technology cannot provide scheduled intermittent boluses in addition to the patient-controlled demand bolus.Lim et al. 11reported another adaptation of epidural delivery pump technology. Their center has developed a computer-integrated PCEA system (CI-PCEA) that controls background infusion rates depending on the previous hour's demand boluses. This randomized trial compared a standard PCEA technique of 0.1% ropivacaine with fentanyl administered as bolus-only by patient demand to the CI-PCEA technique that initiated an infusion algorithm with changing infusion rates depending on demand boluses. Despite patients with the CI-PCEA technique receiving background infusions, the hourly consumption of ropivacaine was no different from that of the standard group (mean PCEA bupivacaine consumption of 7.2 [SD 2.6] mg/h compared with mean CI-PCEA 7.9 [SD 2.9] mg/h). Patient satisfaction was statistically greater the CI-PCEA however, both groups seemed with their (mean visual analog for satisfaction with PCEA [SD compared with CI-PCEA [SD These two studies that there is for in administering epidural for women with to to the literature of epidural analgesia and effect on the of labor is a randomized trial by et al. evaluated term women in early labor. These at the time of request for epidural analgesia, were assigned to initiation of epidural analgesia or a of 4 The of delivery was not different between the with the incidence of delivery 70% in vaginal delivery and and cesarean delivery and The is this population's results are to North the cesarean delivery rates for women in labor are greater than may between the study population and North on as the mean age of the study population was not mean fetal from the study were with a fetal weight greater than and incidence of The between these and and cesarean delivery rates is not articles addressed the use of for cesarean delivery randomized the anesthetic sensory of local anesthesia given through a as compared with a of two randomized women not in the women in both studies parturients received 10 bupivacaine in the through a technique of to and of or a The sensory level was of to ice with results for both studies, shown in table investigators that block between the two techniques only among women not in labor. women not in labor, the block was almost five higher than the The time to the sensory block was also longer in the group (mean min compared with min in the the two anesthetic techniques did not a difference in block The that labor the epidural and the effect the of technique has on changing of local anesthetic The technique is difficulties are in the epidural or however, seems that anesthesiologists into a women is in labor to determine the dose of local anesthetic another et al. the that sequential anesthesia for cesarean delivery is a to than anesthesia. anesthesia is the administration of a dose of followed by epidural block are achieved. The of was studied in women scheduled to elective cesarean delivery a of cardiac The is based on of aortic Women who were randomly assigned to the sequential group had sensory than women with the standard technique compared with however, there were no differences in the cardiac or between the two groups. In both mean was reduced from after 20 and cardiac increased 10 min after of anesthesia. The time to achieve anesthesia was longer in the group receiving sequential and this group more epidural hypotension during cesarean anesthesia is a topic of research because of and cesarean delivery rates. in the of system specifically the between and has to heart rate to the of between may the in the incidence of hypotension and may at increased risk for In a randomized study heart rate before elective cesarean delivery, et al. that women with increased would from or before women with of greater than received a standard anesthetic or or administration of anesthesia for elective cesarean delivery. therapy of a of up to ml before anesthesia or infusion of therapy after induction of anesthesia. of women receiving standard anesthetic with had compared with receiving therapy and receiving the group receiving therapy had their reduced to a of less than This particular technology each and was of an seems to be an for delivery with cesarean delivery rates and the of use of general anesthesia for cesarean delivery is the patients who require or general anesthesia to be with significant medical articles evidence for the induction with particular attention with a study et al. the effect of induction used for The that were evaluated were or which were given in addition to the standard and induction The use of 1.5 in addition to and did not prevent in mean arterial or heart rate at and min after However, the addition of 1 did prevent the at and for the use of in obstetrics has been including use for patient-controlled analgesia during labor and of use during general anesthesia. In a randomized, double-blind study by et al. was compared with during general anesthesia induction for elective cesarean delivery in 40 The standard induction group received 4 and whereas the group received 1 in addition to the and in mean arterial and heart rate were greater in the standard therapy group, between and 7 min after An was the effect of on the and because the Two in the group administration because of at as compared with in the standard induction It seems that may be to maternal at induction and but should be available to provide neonatal therapy at of articles in 2006 were with maternal a of maternal morbidity in developed and maternal in developing countries. 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The that received had 30% to time to first compared with bupivacaine were increased in the group compared with and cardiac bupivacaine content was one of The by the current in the is to bupivacaine events with supportive as well as to 1 followed by ml of obstetric anesthesiologists in the period with the addition of as and to our operative neuraxial The interest in postpartum analgesia has further developed with analgesic techniques and for The use of analgesia techniques than after cesarean delivery has been to local anesthetic of the patient-controlled analgesia, and including et al. another analgesic that of an with intermittent local anesthetic boluses. In this randomized, double-blind analgesia by a was compared with intermittent epidural local anesthetic boluses in 40 women after cesarean delivery. In the after women in the epidural group had pain scores less than the group out of but after this the two groups were no different with to pain scores at rest and at and This can be placed by obstetric at the of and is epidural or postpartum analgesia is pain has been associated with the of and identifying the at risk for pain or increased analgesic requirements would be et al. to our of delivery pain and analgesic use in and of before The women in this study were evaluated 2 before cesarean delivery for including pain and pain during pregnancy, of pain and The different pain outcomes, including pain on pain analgesia, analgesia, and analgesia, were by a of factors than However, less than 30% of in pain outcomes was by the It will be to these in their of these which may of an number of articles to health for pregnant women the women in developing during labor and delivery, their often not with delivery. 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